From Mekong Giant Catfish (Pangasianodon Gigas Chevey) from Mekong River, Chiangrai Province

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Two species of Prosorhynchoides Dollfus, 1929 (Bucephalidae: Bucephalinae) from Mekong giant catfish (Pangasianodon gigas Chevey) from Mekong River, Chiangrai Province

Watchariya Purivirojkul1 and Prapaisiri Sirikanchana2

Abstract Purivirojkul, W. and Sirikanchana, P. Two species of Prosorhynchoides Dollfus, 1929 (Bucephalidae: Bucephalinae) from Mekong giant catfish (Pangasianodon gigas Chevey) from Mekong River, Chiangrai Province Songklanakarin J. Sci. Technol., 2006, 28(4) : 745-751

Two species of bucephalids were found in intestine of Mekong giant catfish (Pangasianodon gigas Chevey) collected from Mekong River, Chiang Khong district, Chiangrai Province. Prosorhynchoides sp.1 is characterised by a rhynchus without tentacle. The tegument covered with spines. The mouth opening is located posteriorly third of body, opening into sac-like intestine. Ovary is pretesticular. Testis is slightly larger than ovary. Prosorhynchoides sp.2 is different from Prosorhynchoides sp.1 in not having spine on the tegument and the presence of two groups of spines adjacent to both sides of the rhynchus; the size of the ovary and testes is almost equal.

Key words : Pangasianodon gigas, parasite, Mekong river, Thailand, Prosorhynchoides

1M.S.(Fisheries Science), Department of Zoology, Faculty of Science, 2M.S.(Zoology), Assoc. Prof., Department of Fishery Biology, Faculty of Fisheries, Kasetsart University, Chatuchak, Bangkok 10900 Thailand. Corresponding e-mail : [email protected] Received, 21 July 2005 Accepted, 23 January 2006 Songklanakarin J. Sci. Technol. Prosorhynchoides Dolfus, 1929 from Mekong giant catfish Vol.28 No.4 Jul. - Aug. 2006 746 Purivirojkul, W. and Sirikanchana, P. ∫∑§—¥¬àÕ «—™√‘¬“ ¿Ÿ√’«‘‚√®πå°ÿ≈1 ·≈– ª√–‰æ ‘√‘ ‘√‘°“≠®π2 ª√ ‘µ„π °ÿ≈ Prosorhynchoides Dollfus, 1929 (Bucephalidae: Bucephalinae) ∑’Ëæ∫„πª≈“∫÷° (Pangasianodon gigas Chevey) ®“°·¡àπÈ”‚¢ß ®—ßÀ«—¥‡™’¬ß√“¬ «. ß¢≈“π§√‘π∑√å «∑∑. 2549 28(4) : 745-751 º≈°“√»÷°…“æ∫ª√ ‘µµ—«·∫π 2 ™π‘¥„π°≈ÿà¡ bucephalids (Digenea: Bucephalidae) „π≈”‰ â¢Õßª≈“∫÷° (Pangasianodon gigas Chevey) ®“°·¡àπÈ”‚¢ß Õ”‡¿Õ‡™’¬ß¢Õß ®—ßÀ«—¥‡™’¬ß√“¬ ‰¥â·°à Prosorhynchoides sp.1 ¡’ ≈—°…≥–‡¥àπ§◊Õ rhynchus ‰¡à¡’Àπ«¥ (tentacle) º‘«µ—«ª°§≈ÿ¡¥â«¬Àπ“¡ ™àÕßª“°Õ¬Ÿà§àÕπ‰ª∑“ß¥â“π∑â“¬¢Õß≈”µ—« ≈”‰ â¡’≈—°…≥–‡ªìπ∂ÿß √—ß‰¢àÕ¬Ÿà∑“ß¥â“πÀπâ“¢ÕßÕ—≥±– ¡’¢π“¥‡≈Á°°«à“Õ—≥±–‡≈Á°πâÕ¬ ·≈–ª√ ‘µ Prosorhynchoides sp.2 ´÷Ëßµà“ß®“° Prosorhynchoides sp.1 ‚¥¬®–‰¡à¡’Àπ“¡∫√‘‡«≥º‘«µ—« ·µà¡’°≈ÿà¡¢ÕßÀπ“¡ 2 °≈ÿà¡Õ¬Ÿà∫√‘‡«≥ 2 ¢â“ß ¢Õß rhynchus ´÷Ëß‰¡àæ∫Àπ“¡ 2 °≈ÿà¡„π Prosorhynchoides siamensis n. sp. ·≈–√—ß‰¢à¡’¢π“¥„°≈â‡§’¬ß°—∫Õ—≥±– 1¿“§«‘™“ —µ««‘∑¬“ §≥–«‘∑¬“»“ µ√å 2¿“§«‘™“™’««‘∑¬“ª√–¡ß §≥–ª√–¡ß ¡À“«‘∑¬“≈—¬‡°…µ√»“ µ√å ®µÿ®—°√ °√ÿß‡∑æœ 10900

Mekong giant catfish, Pangasianodon gigas, translocated to new places (Lerssutthichawal, is the largest freshwater catfish of the world. The 1999). Mekong giant catfish can only be naturally found Some scientists have studied ectoparasites along the Mekong River. Mekong giant catfish is in Mekong giant catfish; 2 isopods were found an endangered species in Convention on Inter- from gill and skin of Mekong giant catfishes, national Trade in Endangered Species of wild fauna namely Alitropus typus and Corallana grandiventra and flora (CITES). The number of this fish caught (Thonguthai, 1991). No monogenean species were in Thailand at Chiang Khong district, Chiangrai found on P. gigas (Lerssutthichawal, 1999). How- province, has decreased from 69 fishes in 1990 to ever, there are no reports about endoparasites in 20 fishes in 1999 (Mengumphan, 2000). In 2005, P. gigas. So the result from this study will be useful only 2 fishes were caught. This indicated that the as the basic data for management Mekong giant population of the Mekong giant catfish has catfish resource in the future. decreased rapidly because the male and female spawners were heavily caught. Most of caught Materials and Methods fishes were sold to restaurant and in the market at a very high price. However, a breeding program of Three males and three females of Mekong this fish species has been successfully implemented giant catfish (Pangasianodon gigas) caught in (Mengumphan, 2000). The Department of Fisheries 2004-2005 from the Mekong River, Chiang Khong released Mekong giant catfish larva to many District, Chiangrai Province were used in the reservoirs. For ecological reasons, the Mekong giant study. Weight of the males was 152, 159, 213 catfish is considered as an exotic or introduced while the females were 252, 225 and 287 kilo- species in some rivers, and might be the cause of grams. The total length of these fishes were 2.3, some changes in the ecology of the rivers. The most 2.3, 2.3, 2.5, 2.32 and 2.68 meters, respectively. important change concerns the parasite outbreak The fish were examined for intestinal parasites. caused from the released giant catfishes to the The intestine was removed from body cavity and same or related species fishes in the natural aquatic the contents were then examined under the micro- habitat and/or from the fishes in natural basins to scope. The parasites collected were fixed in 70% the released fishes. Parasites have been dispersed ethanol for 24 hours. Specimens were stained with along with their fish hosts when the fish are Mayer's hydrochloric carmine, dehydrated and Songklanakarin J. Sci. Technol. Prosorhynchoides Dolfus, 1929 from Mekong giant catfish Vol.28 No.4 Jul. - Aug. 2006 747 Purivirojkul, W. and Sirikanchana, P. mounted in Canada balsam. spines except posterior region (about 1/6 of body Measurements of the parasites were given length from posterior). Rhynchus sucker-like, in micrometers, with their ranges and averages. anterior end of body, size 169-262 x 161-250 (211 Drawings were made with the aid of a camera x 202) µm. The mouth opening posterior third of lucida device. Photography of whole specimens body, leading to the pharynx and sac-shaped were carried out by using a binocular microscope. intestine. Pharynx spherical, 97-150 x 99-153 (121 The specimens were deposited at Aquatic x 124) µm. Intestinal caecum short, sac-like, 363- Parasitology Collection of Department of Zoology, 605 x 97-182 (461 x 136) µm. Gonads middle third Kasetsart University, Thailand. Identification and of body. The ovary pretesticular, spherical shape, classification of the species were done using 193-277 x 161-248 (238 x 196) µm. Two oval Yamaguti (1958), Bykhovskaya - Pavlovskaya et testes, 227- 350 x 134-211 (284 x 172) µm were al. (1964), Hoffman (1970) and Overstreet and oblique in posterior half of body. Cirrus sac long, Curran (2002) 299-462 x 63-102 (376 x 79) µm. Seminal vesicle oval, 106-165 x 48-73 (133 x 59) µm. Pars Results prostatica straight, 162-257 x 23-37 (208 x 29) µm. Cirrus projected into genital atrium near posterior Two species of parasites were found in the end of body. Vitellaria situated near the sucker, intestine of Mekong giant catfishes. Both were in consisted of 11-14 large follicles. Uterus loops genus Prosorhynchoides (Digenea:Bucephalidae). extend from under the muscular sucker to the Prosorhynchoides sp.1 was found in all fish posterior end of testis, containing numerous golden samples, while Prosorhynchoides sp.2 was found brown, operculate- eggs, oval shaped, 14-21 x 5-8 in two fishes caught in the year 2005. The number (17 x 6) µm. The excretory vesicle not observed. of specimens collected is shown in Table 1. The excretory pore was found at posterior end. Prosorhynchoides sp.1 in each sample was between Data regarding specimens 25-240 and the number of Prosorhynchoides sp.2 Type host: Mekong giant catfish (Panga- in each sample was between 4-12. Morphological sianodon gigas Chevey) details of the parasites examined are given below. Site of infection: intestine Type locality: 100º 24′ 38′′ S; 20º 15′ 50′′ 1. Prosorhynchoides sp.1 (Figure 1) E, Mekong River, Chiang Khong district, Chiang Description Rai Province, Thailand. Body very small, elliptical, with maximum Number of parasite examined : 10 width at post-oral region, 1100-1700 x 554-857 Type depository: Holotype KUSCID 4701 (1373 x 692) µm. The tegument was covered with

Table 1. Mekong Giant Catfish biological data and number of parasites, Prosorhynchoides sp.1 and Prosorhynchoides sp.2 from each fish.

No. Caught Sex Weight Length Number of Number of date (kg) (m) Prosorhynchoides sp.1 Prosorhynchoides sp.2 1 29/4/2004 Male 152 2.3 240 0 2 30/4/2004 Male 159 2.3 206 0 3 2/5/2004 Female 252 2.5 36 0 4 6/5/2004 Female 225 2.32 25 0 5 27/4/2005 Male 213 2.3 238 4 6 1/5/2005 Female 287 2.68 221 12 Songklanakarin J. Sci. Technol. Prosorhynchoides Dolfus, 1929 from Mekong giant catfish Vol.28 No.4 Jul. - Aug. 2006 748 Purivirojkul, W. and Sirikanchana, P.

2. Prosorhynchoides sp.2 (Figure 2) of spines were situated laterally of the rhynchus. Description Each group consisted of 10-12 spines with various Body very small, elliptical, with maximum sizes between 26-83 (55) µm in length. The mouth width at post-oral region, 1140-1670 x 552-864 opening was at the posterior third of body, leading (1412 x 709) µm. The tegument without spines. to the pharynx and sac-shaped intestine. Pharynx Rhynchus sucker-like was at anterior end of body, spherical, 83-147 x 83-141 (115 x 112) µm. 145-237 x 140-230 (190 x 185) µm. Two groups Intestinal caecum sac-like, short, 307-499 x 130-

Figure 1. Prosorhynchoides sp.1 (1) photograph (2) drawing; Scale-bar 0.5 mm.

Figure 2. Prosorhynchoides sp.2 (1) photograph (2) drawing; Scale-bar 0.5 mm. (3) spine; Scale-bar 0.1 mm. Songklanakarin J. Sci. Technol. Prosorhynchoides Dolfus, 1929 from Mekong giant catfish Vol.28 No.4 Jul. - Aug. 2006 749 Purivirojkul, W. and Sirikanchana, P.

184 (403 x 153) µm. Gonads located at middle In Mekong river, Prosorhynchoides graci- third of body. The spherical ovary pretesticular, lescens was reported in fish from the Cuulong river 129-192 x 138-198 (161 x 169) µm. Two testes (Te, 1998). The morphology of these two species ovoid 151- 205 x 140-202 (175 x 172) µm were was similar to P. gracilescens and P. pusilla. In oblique in posterior half of the body. Cirrus sac Laos, Scholz (1991) found P. karvei in Xenentodon long, 417-640 x 61-90 (529 x 73) µm. Seminal cancila intestine from Nam Ngum reservior. vesicle oval, 107-154 x 50-77 (128 x 64) µm. Pars However, the size of rhynchus compared with prostatica straight, 241-416 x 18-26 (327 x 22) body size of P. karvei was very different from that µm. Cirrus projected into genital atrium near in these two species. posterior end of body. Vitellaria located latterally Prosorhynchoides sp.1 and Prosorhyn- of the sucker, consisted of 14 large follicles. Uterus choides sp.2 are placed in family Bucephalidae, loops occupying from under the muscular sucker genus Prosorhynchoides Dollfus, 1929 (Syns.: to the posterior end of testis, containing numerous Bucephalopsis Diesing, 1855; Neobucephalopsis golden brown operculate-eggs, oval shaped, 14-22 Dayal, 1948; Bucephaloides Hopkins, 1954) x 5-8 (18 x 7) µm. The excretory vesicle was not according to the rhynchus not having tentacle. The observed. The excretory pore was found at posterior mouth is on the midventral surface of body, open- end. ing into the sac-like intestine. Ovary pretesticular. Data regarding specimens Seminal receptacle absent. Two testis oblique. Type host: Mekong giant catfish (Panga- Cirrus-sac conspicuous, located posteriorly, sianodon gigas Chevey) containing internal seminal vesicle and male duct. Site of infection: intestine Male duct consisting of extensive pars prostatica Type locality: 100º 24′ 38′′ S; 20º 15′ 50′′ and distal ejaculatory duct leading into genital E, Mekong River, Chiang Khong district, Chiang atrium. Uterus usually coiling throughout the body. Rai Province, Thailand. Distal portion of uterus entering genital atrium. Number of parasite examined : 10 Vitelline follicle located in fore body. These two Type depository: Holotype KUSCID 4802 species are also morphologically different from P. gracilescens (Rudolphi, 1819) of salmonid fish Discussion (Bykhovskaya - Pavlovskaya et al., 1964) and P. pusilla (Stafford, 1904), which was found in the In our study, we found ectoparasite, Alitropus intestine of Stizostedion vitreum, Micropterus typus as reported by Tonguthai (1991) but did not dolomieui, Etheostoma nigrum, Lepomis cyanellus, find any monogean. However, Alitropus typus is L. humilis, Pimephales promelas, Esox lucius, not specifically found only in P. gigas, it could Ictalurus melas, Perca flavescens (Bangham,1944, found commonly in many species of fishes from 1955; Cooper, 1951; Hoffman, 1970; Lyster, 1939; water resource (Tonguthai, 1991). We did not find Meyer, 1958; Van Cleave and Mueller, 1934). The any endoparasite in P. gigas muscle, only two mouth opening positions of P. gracilescens and P. species of digenetic trematodes in family pusilla are about half of the body length while in Bucephalidae were found in the P. gigas intestine. Prosorhynchoides sp.1 and Prosorhynchoides sp.2 The Bucephalidae Poche, 1907 are digenetic are about 2/3 of body length. The presence of trematodes found in the intestines of marine, spines on the tegument and near the rhynchus brackish water and freshwater fishes. Bucephalids are two remarkable differences of these two differ from all other digeneans in the configuration Prosorhynchoides species (Table 2). In author's of their terminal genitalia, the presence of a opinion, Prosorhynchoides sp.1 and Prosorhyn- ventrally located mouth and the presence of as choides sp.2 might be new species because they anterior attachment rhynchus that is not associated differ from the previously described species of this with the digestive system (Bott and Cribb, 2005). genus. Songklanakarin J. Sci. Technol. Prosorhynchoides Dolfus, 1929 from Mekong giant catfish Vol.28 No.4 Jul. - Aug. 2006 750 Purivirojkul, W. and Sirikanchana, P.

Table 2. Morphology difference between Prosorhynchoides sp.1, Prosorhynchoides sp.2, P. gracilescens and P. pusilla.

Morphology Prosorhynchoides sp.1 Prosorhynchoides sp.2 P. gracilescens P. pusilla Length 0.84-1.02 mm. 1.14-1.67 mm. 1.2-2.2 mm. 0.79 mm. Width 0.42-0.55 mm. 0.55-0.86 mm. 0.4-0.7 mm. 0.23 mm. Size of 0.21 x 0.2 mm. 0.19 x 0.19 mm. 0.185 x 0.205 mm. 0.13 x 0.14 mm muscular sucker Position of 2/3 from anterior 2/3 from anterior 1/2 from anterior 1/2 from anterior mouth opening Pharynx 0.05 mm. Wide 0.121 mm. Wide 0.125 mm. Wide 0.04 mm. Wide 0.07 mm. long 0.124 mm. long 0.09 mm. Long 0.04 mm. long Ratio of intestine 5.3 : 1 2.54 : 1 1.43 : 1 1.79 : 1 length: width Ratio ovary : testis 2 : 3 1 : 1 2 : 3 1 : 1 Ratio of testis 2.45 : 1 1 : 1 1.5 : 1 1 : 1 length: width Egg 0.015-0.021 x 0.014-0.022 x 0.018-0.029 x 0.017-0.019 x 0.005-0.007 mm. 0.005-0.008 mm. 0.013-0.021 mm. 0.009-0.01 mm. Has group of spine - + - - laterally of the rhynchus Organ Intestine Intestine Intestine,stomach, Intestine Pyrolic caeca

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